Telephone system.



I. N. WALLACE.

TELEPHONE SYSTEM.

mncnlon FILED MAR. 22, 1 09.

Patented Nuv. 23,1909.

M MM. ,m m

JoHir N. wALnA'ca-or LA cnossn, WISCONSIN, Assmnoa TO vozrn nnnennCOMPANY,

'I To all wlwm concern:

or LA v ciaossri, WISCONSIN.

TELEPHONE SYSTEM.

- Be it known h JOHN N; WALLACE a subject-of the King of England, and aresident ofLa Grosse,-county of La Crosse, and Statebf Wisconsin, haveinvented anew and useful Improvement in Telephone Systems,

of which the following is a specification.

' invention pertains. to telephone sysjtemsusing'visu'al signals of thelamp type,

as used in telephone switchboards, and it comprises animprovement insuch systems,

whereby "inmy improved system the signal is adapted in itself toresponddirectly to variant conditions of control whlch heretofore'have requiredauxiliaryor additional -duced at firstinto the telephone switchboard asa visual signal-for the operator, it was applied by including the hel xof a relay in the controlling circuit and relaying the control by meansof contacts controlled by the helix, whereby the lamp and contacts and.

the source of current could be included in a circuit local to thecentral office, all such cirternal conditions of the main circuit towhich the signal pertained, and of which its controlling helix' formed acomponent part.

This-method ,of contrdlling the lamp filashall fall within rather narrowlimits. current may be produced only by potentials nient'wasnecessarybecause the lamps were notlada ted to operate successfully whenincluded directly in circuits which might be closed through widelyvarying series resistances. h

The carbon lncandescent filament requires far its proper illumination acurrent which which fall within still narrower limits, since ,.i thecarbon filament itself manifests the i when subjected to an increasingelec-.

characteristic of a decreasing reslstance I tromotiv'e force.Furthermore, the variation-of the illumination, is greater than the]variation of the current, and has Specification'of Letters Patent.Applicationfiled March 22, 1909. Serial No. 484,871.

This

, P atented' Nov. 23, 1909.

a still higher ratio to the. impressed petential; the carbon filamentincandescent lamp included directly in circuits with Vanable seriesresistance having widely variable values therefore became an inadvisableapplication of the device. Particularly was this limitation felt inconnection with the carbon filament lamp for use as a'li'ne signal wherelines approached considerable resistances,- because of the ossibleaccidental -short-circuiting of the lines within or near the centraloffice, which action would reduce the external line resistance to zeroand give to the carbon filament of the lamp substanquently destroyingthem on the first occa-' sion. In connection with the use of the carbonfilament incandescent lamp for signal-- ing purposes in such circuits,so calledbaL lasting in two ways has been resorted'to. The first methodof ballasting is the inclusion in'the circuit with thelamp and adj acentto the lamp, or betweenthe source of potential and the lamp, ofadead'resistance tially the entire potential of the central oflicesource of energy. This resulted in reducing the life of lamps sosubjected, very freso high that the resistance of the external andvariable portion of the circuit would become negligible, orwould-produce at most a maximum current variation in the circuit whichWouldfa-ll within the limitations of the current-carryingcapacity of thelamp filament. The objection to this method of ballasting resistance.From.7 5% to 90% of the total energy used for signaling purposes isrequired as a ballastingloss in such an arrangement. g I The secondmethod of ballasting is to include in series with the carbon lamp aballasting resistance manifesting to a high degree the characteristicof, an increasing resistance when suo ected to anincreasingelectromotive force,

Such a ballast offers 5 resistance, but ofiers a higher resistance whenthe external variable resistance is low,

by reason of the higher drop of potential across the ballast under sucha condition.-

An arrangement of this second method of ballastmg comprises merely aniron filament in series "with the carbon filament, both preferably invacuum,, in. order that the iron filament may attain incandescencewithoutcombustion.

In my improved,signalingsystem for tele-.

phone exchanges, Iprovide, in connection with the signaling andswitching circuits of the telephone system, an incandescent lampfilament manifesting within itself the characteristic of presenting anincreasing resistance to an increasing electromotiveforce, therebymanifesting w-ithm itself the.

characteristics heretofore obtained only by the conjunction of anincandescent filament and a ballast resistance of 'the second class,above described. Such an incandescent filament may be'formed of tantalumor tungsten, or metals manifesting similai' characteristics. Theresistance of the lamp in my system of signaling preferably is high, in

order that the total variation bycontrol of the external circuit may bea minimum, thereby attaining also the advantages of the first mentionedmethod of ballasting but without the objectionable loss of energy,

since all energy is consumed in the signal lamp. j j

I illustrate the circuits of my invention in the figure accompanying,showing therein the simplest typical circuits in'which my invention maybe embodied. It is obvious,

that in addition to the line circuit shown,

my invention may be applicable to many signaling circuits throughout theexchange installation. j p

In the figure, a circuit extends from earth through the battery Land thenietalliofilament of lamp 2, thence 'through contact of relay 3, andthrough line conductor 4, substation 5, line conductor 6, and remainingcontact of relay 3 to earth. It will be seen that'the filament of lamp 2is subjected to currents of minimum strength when the line is in goodcondition and the receiver at 5 is lifted, and that it is subjected tocurrents 'of maximum strength when for anyreason the conductors I and 6are connected I at a pointnear the jack-7. The filament of the lamp-2being a metallic filament, with a positive heat'co-etficient, willcompensate.

to some degree by the variationof'its .own

resistance for any variation of the resistance in the conductors of theline. .I-

By insertion of the plug 8 in the-jack 7, i lay' twill the battery9'will find, circuit throug% signal circuits in many instancesjw'ill' beI possible by the use of the combination of controlling resistances anda lamp having imam apositive heat co-eflicient in instances otherillustration. Having thus described "States Letters Patent is: r

1. In aftelephone system, a line circuit containing a netallic filamentlamp, and means for opening and closing said line circuit, substantiallyas described. 2. Ina telephone system, a circuit containinga metallicfilament lamp and means for opening and closing the circuit, saidcircuit having variant resistance values when closed, substantially-asdescribed.

3. I11 a telephone system, a battery; a metallic filament lamp; and atelephone line circuit in series therewith, substantially as described.

4. In a telephone system, a -line signal comprising a metallic filamentlamp con- I nected directly between a source of potential and theswitching devices of a line equipment, and included in a circuit withthe line conductors, substantially as described.

5. In a telephone system, a line signal eluded directly in circuit withthe line and sub-station equipment, substantially as de; scribed.

cient" of resistance and means for opening and closing the circuit,-saidcircuit'having variant resistance values when closed, sub stantially asdescribed. i

7. In a telephone system, a battery; a signal lamp having a positivecoefficient of resistance; and a telephone line; said elements inseries, substantially as described.

8. In a telephone system, a line signal coefiicient of resistance andconnecteddiswitching, devices of a Hneiequipment and tially asdescribed.

- '9. In a telephone system, a' line; signal equipment, substantially asdescribed.

alpluralityg of telephone lines to any one "of which any one of saidlamps may-be connected in series with the line and the battery,substantially as described.

T 11. atelephone system, a plurality of telephone lines of variantresistances a pluthan the one specific case here. shown for j invention,what. I claim as new and desire to secure by United comprising a lamphaving a positiveheat" comprising a signal lamp having a-pos'itive heatcoeflicient of resistance and included directly in circuit with the-lineand substation 1'15 '10. In telephone system, r plurality"of,signal-lamps, all alike, and having a positive "heat coeflicient-ofresistance; a battery; and" comprising a metallic filament. lamp ino. Ina telephone system, a circuit containing a lamp having a positive heatcoeffi-- rectly between a source of potential and the included in seriesin a circuit with thelin'e conductors and substation bridge,substan-vrality of ianips (if uniform electrical'characteristics and having tpositive heat e0efli-'- clent of resistance; and "a' battery j said 7rality of lamps, and similar, and having metallic filaments; and asourceof current; 10 each bf said lines being in series with one of said lampsand said 'source,--substantia11y as described.

Signed by me at La Crosse, county of La Crosse and State of Wisconsin,in the presence' of the two Witnesses.

. JOHN N.- WALLACE.

Witnesses: I

GUST.'.I. LUNDGREN, LOREN S. BEEs.

